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// Copyright 2021 Parity Technologies (UK) Ltd.
// This file is part of Parity Bridges Common.
// Parity Bridges Common is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Parity Bridges Common is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Parity Bridges Common. If not, see <http://www.gnu.org/licenses/>.
//! Substrate GRANDPA Pallet
//! This pallet is an on-chain GRANDPA light client for Substrate based chains.
//! This pallet achieves this by trustlessly verifying GRANDPA finality proofs on-chain. Once
//! verified, finalized headers are stored in the pallet, thereby creating a sparse header chain.
//! This sparse header chain can be used as a source of truth for other higher-level applications.
//! The pallet is responsible for tracking GRANDPA validator set hand-offs. We only import headers
//! with justifications signed by the current validator set we know of. The header is inspected for
//! a `ScheduledChanges` digest item, which is then used to update to next validator set.
//!
//! Since this pallet only tracks finalized headers it does not deal with forks. Forks can only
//! occur if the GRANDPA validator set on the bridged chain is either colluding or there is a severe
//! bug causing resulting in an equivocation. Such events are outside the scope of this pallet.
//! Shall the fork occur on the bridged chain governance intervention will be required to
//! re-initialize the bridge and track the right fork.
#![cfg_attr(not(feature = "std"), no_std)]
// Runtime-generated enums
#![allow(clippy::large_enum_variant)]
use storage_types::StoredAuthoritySet;
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use bp_header_chain::{justification::GrandpaJustification, InitializationData};
use bp_runtime::{
BlockNumberOf, BoundedStorageValue, Chain, HashOf, HasherOf, HeaderOf, OwnedBridgeModule,
};
use finality_grandpa::voter_set::VoterSet;
use frame_support::{ensure, fail};
use sp_finality_grandpa::{ConsensusLog, GRANDPA_ENGINE_ID};
use sp_runtime::traits::{Header as HeaderT, Zero};
use sp_std::{boxed::Box, convert::TryInto};
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mod extension;
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mod storage_types;
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/// Module, containing weights for this pallet.
pub mod weights;
#[cfg(feature = "runtime-benchmarks")]
pub mod benchmarking;
// Re-export in crate namespace for `construct_runtime!`
pub use pallet::*;
pub use weights::WeightInfo;
/// The target that will be used when publishing logs related to this pallet.
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pub const LOG_TARGET: &str = "runtime::bridge-grandpa";
/// Block number of the bridged chain.
pub type BridgedBlockNumber<T, I> = BlockNumberOf<<T as Config<I>>::BridgedChain>;
/// Block hash of the bridged chain.
pub type BridgedBlockHash<T, I> = HashOf<<T as Config<I>>::BridgedChain>;
/// Hasher of the bridged chain.
pub type BridgedBlockHasher<T, I> = HasherOf<<T as Config<I>>::BridgedChain>;
/// Header of the bridged chain.
pub type BridgedHeader<T, I> = HeaderOf<<T as Config<I>>::BridgedChain>;
/// Stored header of the bridged chain.
pub type StoredBridgedHeader<T, I> =
BoundedStorageValue<<T as Config<I>>::MaxBridgedHeaderSize, BridgedHeader<T, I>>;
#[frame_support::pallet]
pub mod pallet {
use super::*;
use bp_runtime::BasicOperatingMode;
use frame_support::pallet_prelude::*;
use frame_system::pallet_prelude::*;
#[pallet::config]
pub trait Config<I: 'static = ()>: frame_system::Config {
/// The chain we are bridging to here.
type BridgedChain: Chain;
/// The upper bound on the number of requests allowed by the pallet.
///
/// A request refers to an action which writes a header to storage.
///
/// Once this bound is reached the pallet will not allow any dispatchables to be called
/// until the request count has decreased.
#[pallet::constant]
type MaxRequests: Get<u32>;
/// Maximal number of finalized headers to keep in the storage.
///
/// The setting is there to prevent growing the on-chain state indefinitely. Note
/// the setting does not relate to block numbers - we will simply keep as much items
/// in the storage, so it doesn't guarantee any fixed timeframe for finality headers.
///
/// Incautious change of this constant may lead to orphan entries in the runtime storage.
#[pallet::constant]
type HeadersToKeep: Get<u32>;
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/// Max number of authorities at the bridged chain.
#[pallet::constant]
type MaxBridgedAuthorities: Get<u32>;
/// Maximal size (in bytes) of the SCALE-encoded bridged chain header.
///
/// This constant must be selected with care. The pallet requires mandatory headers to be
/// submitted to be able to proceed. Mandatory headers contain public keys of all GRANDPA
/// authorities. E.g. for 1024 authorities, the size of encoded keys will be at least 32 KB.
/// The same header may also contain other digest items as well, so some reserve here
/// is required.
#[pallet::constant]
type MaxBridgedHeaderSize: Get<u32>;
/// Weights gathered through benchmarking.
type WeightInfo: WeightInfo;
#[pallet::pallet]
pub struct Pallet<T, I = ()>(PhantomData<(T, I)>);
#[pallet::hooks]
impl<T: Config<I>, I: 'static> Hooks<BlockNumberFor<T>> for Pallet<T, I> {
fn on_initialize(_n: T::BlockNumber) -> frame_support::weights::Weight {
<RequestCount<T, I>>::mutate(|count| *count = count.saturating_sub(1));
(0_u64)
.saturating_add(T::DbWeight::get().reads(1))
.saturating_add(T::DbWeight::get().writes(1))
}
}
impl<T: Config<I>, I: 'static> OwnedBridgeModule<T> for Pallet<T, I> {
const LOG_TARGET: &'static str = LOG_TARGET;
type OwnerStorage = PalletOwner<T, I>;
type OperatingMode = BasicOperatingMode;
type OperatingModeStorage = PalletOperatingMode<T, I>;
impl<T: Config<I>, I: 'static> Pallet<T, I> {
/// Verify a target header is finalized according to the given finality proof.
/// It will use the underlying storage pallet to fetch information about the current
/// authorities and best finalized header in order to verify that the header is finalized.
///
/// If successful in verification, it will write the target header to the underlying storage
/// pallet.
#[pallet::weight(T::WeightInfo::submit_finality_proof(
justification.commit.precommits.len().try_into().unwrap_or(u32::MAX),
justification.votes_ancestries.len().try_into().unwrap_or(u32::MAX),
origin: OriginFor<T>,
finality_target: Box<BridgedHeader<T, I>>,
justification: GrandpaJustification<BridgedHeader<T, I>>,
) -> DispatchResultWithPostInfo {
Self::ensure_not_halted().map_err(Error::<T, I>::BridgeModule)?;
ensure!(Self::request_count() < T::MaxRequests::get(), <Error<T, I>>::TooManyRequests);
let (hash, number) = (finality_target.hash(), finality_target.number());
log::trace!(
target: LOG_TARGET,
"Going to try and finalize header {:?}",
finality_target
);
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let best_finalized = BestFinalized::<T, I>::get();
let best_finalized =
best_finalized.and_then(|(_, hash)| ImportedHeaders::<T, I>::get(hash));
let best_finalized = match best_finalized {
Some(best_finalized) => best_finalized,
None => {
log::error!(
"Cannot finalize header {:?} because pallet is not yet initialized",
finality_target,
);
fail!(<Error<T, I>>::NotInitialized);
// We do a quick check here to ensure that our header chain is making progress and isn't
// "travelling back in time" (which could be indicative of something bad, e.g a
// hard-fork).
ensure!(best_finalized.number() < number, <Error<T, I>>::OldHeader);
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